Methods and apparatus taught herein estimate the amount by which to reduce a multi-carrier signal's maximum transmit power based on metrics specific to each carrier of the multi-carrier signal. These carrier-specific metrics may include a maximum-power reduction or cubic metric determined for that carrier as if it would be transmitted alone. In one embodiment, estimation of the required back-off is based on a weighted sum of the carrier-specific metrics, where the weights applied depend on a power ratio. Only a few relatively small look-up tables or simple computations are required in this case: one for obtaining the carrier-specific metrics based on configuration parameters of each carrier, and another for obtaining the weights based on the power ratio. Accordingly, methods and apparatus herein advantageously require less computational complexity and/or memory usage than that needed if estimating the required back-off based on similar metrics obtained for the multi-carrier signal as a whole.
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1. A method in a wireless communication transmitter configured to transmit a multi-carrier signal, the multi-carrier signal being an aggregation of two or more separately modulated carriers occupying distinct frequency regions, comprising: obtaining, for each of the two or more carriers, a carrier-specific metric indicative of an amount by which the maximum transmit power on that carrier should be reduced from a pre-determined nominal maximum transmit power, if transmitted alone, to achieve a pre-determined out-of-band emission requirement; and estimating, by the wireless communication transmitter, a multi-carrier transmitter back-off metric for reducing the multi-carrier signal's maximum transmit power, based on the two or more carrier-specific metrics obtained.
A wireless transmitter uses multiple carriers (different frequency ranges) to send a signal. To avoid transmitting signals outside the allowed frequency bands, the transmitter estimates how much it needs to reduce its maximum power. For each carrier, it determines a "carrier-specific metric." This metric indicates how much the power on that *individual* carrier would need to be reduced, if *only* that carrier were transmitting, to meet emission requirements. The transmitter then uses these individual carrier metrics to estimate the overall power reduction needed for the combined multi-carrier signal.
2. The method of claim 1 wherein obtaining a carrier-specific metric comprises calculating the carrier-specific metric, or retrieving it from a lookup table, based on one or more configuration parameters of a signal on that carrier.
The wireless transmitter, as described above, obtains the "carrier-specific metric" by either calculating it directly based on the configuration of the signal on that carrier, or by looking up a pre-calculated value in a table. This table is indexed by the signal's configuration parameters.
3. The method of claim 2 wherein the one or more configuration parameters comprise gain factors for the physical channels in a Wideband Code-Division Multiple Access (WCDMA) signal, or resource block allocations and modulation scheme in a Long Term Evolution (LTE) signal.
In the wireless transmitter's method, as described above, the "configuration parameters" used to calculate or lookup the carrier-specific metric include: for WCDMA signals, the gain factors of the physical channels; or, for LTE signals, the resource block allocations and the modulation scheme being used.
4. The method of claim 1 wherein obtaining a carrier-specific metric comprises obtaining a cubic metric, a peak-to-average power ratio, or a maximum-power reduction value.
In the wireless transmitter's method, as described above, the "carrier-specific metric" can be a cubic metric, a peak-to-average power ratio (PAPR), or a maximum-power reduction (MPR) value, each calculated for the individual carrier as if it were transmitting alone.
5. The method of claim 1 wherein estimating the multi-carrier transmitter back-off metric is further based on a power ratio between the power of one or more channels on one of the carriers and the power of a corresponding one or more channels on other carriers.
A wireless communication transmitter estimates how much to reduce its total multi-carrier signal power to comply with out-of-band emission requirements. This estimation method involves two main steps for a multi-carrier signal, which is an aggregation of two or more distinct carriers. First, for each individual carrier, the transmitter obtains a "carrier-specific metric." This metric indicates how much that carrier's maximum transmit power would need to be reduced if it were transmitted by itself to achieve the pre-determined emission limits. Second, the transmitter calculates an overall "multi-carrier transmitter back-off metric" for reducing the multi-carrier signal's maximum transmit power. This calculation is based on the previously obtained individual carrier-specific metrics. Additionally, this back-off metric estimation *also takes into account a power ratio*. This power ratio compares the power of one or more channels on one of the carriers to the power of corresponding one or more channels present on other carriers within the multi-carrier signal.
6. The method of claim 5 wherein the power ratio comprises: a ratio between the power of all channels on one of the carriers and the power of all channels on other carriers; or a ratio between the power of a single control channel on one of the carriers and the power of a corresponding control channel on other carriers.
In the wireless transmitter's method, as described above where the power ratio between carriers is considered for back-off estimation, the power ratio can be either the ratio of total power across all channels on one carrier to the total power across all channels on other carriers; or it can be a ratio between specific control channels on different carriers.
7. The method of claim 1 wherein estimating the multi-carrier transmitter back-off metric is further based on one or more configuration parameters of a signal on at least one of the carriers.
In the wireless transmitter's method, as described above, the estimation of the overall power reduction for the multi-carrier signal also considers the configuration parameters of at least one of the carriers. These parameters influence the back-off estimation in addition to the individual carrier metrics.
8. The method of claim 7 wherein the one or more configuration parameters comprise gain factors for the physical channels in a Wideband Code-Division Multiple Access (WCDMA) signal, or resource block allocations and modulation scheme in a Long Term Evolution (LTE) signal.
In the wireless transmitter's method, as described above where carrier configuration parameters are used for back-off estimation, the configuration parameters include, for WCDMA signals, the gain factors of the physical channels; or, for LTE signals, the resource block allocations and the modulation scheme being used.
9. The method of claim 1 wherein estimating the multi-carrier transmitter back-off metric is based on a weighted sum of the two or more carrier-specific metrics obtained.
In the wireless transmitter's method, as described above, the overall power reduction for the multi-carrier signal is estimated by calculating a weighted sum of the carrier-specific metrics. Each individual carrier metric is multiplied by a weight, and these weighted metrics are summed to determine the total back-off.
10. The method of claim 9 wherein the weight applied to each carrier-specific metric is a constant or, alternatively, depends on at least one of: a power ratio between the power of one or more channels on one of the carriers and the power of a corresponding one or more channels on other carriers; or one or more configuration parameters of a signal on at least one of the carriers.
In the wireless transmitter's method, as described above, where a weighted sum of carrier-specific metrics is used to estimate the back-off, the weight applied to each metric can be a fixed constant. Alternatively, the weight can depend on the power ratio between channels on different carriers or on the configuration parameters of at least one of the carriers.
11. The method of claim 9 wherein the weight applied to each carrier-specific metric depends on a power ratio between the power of one or more channels on one of the carriers and the power of a corresponding one or more channels on other carriers, and wherein the method further comprises calculating the weights, or retrieving them from a lookup table, based on the value of the power ratio or, alternatively, based on which one of a plurality of ranges the power ratio falls within.
In the wireless transmitter's method, as described above, where the weight applied to each carrier-specific metric depends on a power ratio between channels on different carriers, the weights are either calculated directly from the power ratio, or looked up in a table based on the power ratio's value or the range within which the power ratio falls.
12. A wireless communication transmitter configured to transmit a multi-carrier signal, the multi-carrier signal being an aggregation of two or more separately modulated carriers occupying distinct frequency regions, comprising: a multi-carrier transmitter back-off metric estimation circuit configured to: obtain, for each of the two or more carriers, a carrier-specific metric indicative of the amount by which the maximum transmit power on that carrier should be reduced from a pre-determined nominal maximum transmit power, if transmitted alone, to achieve a pre-determined out-of-band emission requirement; and estimate a multi-carrier transmitter back-off metric for reducing the multi-carrier signal's maximum transmit power, based on the two or more carrier-specific metrics obtained.
A wireless transmitter is designed to transmit using multiple carriers (different frequency ranges). It includes a special circuit for estimating how much to reduce the maximum transmit power to stay within allowed frequency bands. This circuit first determines a "carrier-specific metric" for each carrier, indicating how much that single carrier's power would need to be reduced, if transmitted alone, to meet emission requirements. Then, it estimates the necessary power reduction for the entire multi-carrier signal based on these individual carrier metrics.
13. The wireless communication transmitter of claim 12 wherein the multi-carrier transmitter back-off metric estimation circuit is configured to obtain a carrier-specific metric by calculating the carrier-specific metric, or retrieving it from a lookup table, based on one or more configuration parameters of a signal on that carrier.
In the wireless transmitter described above, the back-off estimation circuit obtains the "carrier-specific metric" by either calculating it directly based on the configuration of the signal on that carrier, or by retrieving a pre-calculated value from a lookup table.
14. The wireless communication transmitter of claim 13 wherein the one or more configuration parameters comprise gain factors for the physical channels in a Wideband Code-Division Multiple Access (WCDMA) signal, or resource block allocations and modulation scheme in a Long Term Evolution (LTE) signal.
In the wireless transmitter described above, where the back-off estimation circuit calculates or looks up the carrier-specific metric, the "configuration parameters" used include: for WCDMA signals, the gain factors of the physical channels; or, for LTE signals, the resource block allocations and the modulation scheme being used.
15. The wireless communication transmitter of claim 12 wherein the multi-carrier transmitter back-off metric estimation circuit is configured to obtain a carrier-specific metric as a cubic metric, a peak-to-average power ratio, or a maximum-power reduction value.
In the wireless transmitter described above, the back-off estimation circuit obtains the "carrier-specific metric" as a cubic metric, a peak-to-average power ratio (PAPR), or a maximum-power reduction (MPR) value, each calculated for the individual carrier as if it were transmitting alone.
16. The wireless communication transmitter of claim 12 wherein the multi-carrier transmitter back-off metric estimation circuit is configured to estimate the multi-carrier transmitter back-off metric further based on a power ratio between the power of one or more channels on one of the carriers and the power of a corresponding one or more channels on other carriers.
In the wireless transmitter described above, the back-off estimation circuit also considers the power ratio between channels on different carriers when estimating the overall power reduction. The relative power levels of channels on one carrier compared to others influences the back-off.
17. The wireless communication transmitter of claim 16 wherein the power ratio comprises: a ratio between the power of all channels on one of the carriers and the power of all channels on other carriers; or a ratio between the power of a single control channel on one of the carriers and the power of a corresponding control channel on other carriers.
In the wireless transmitter described above, where the back-off estimation circuit uses power ratios between carriers, the power ratio can be either the ratio of total power across all channels on one carrier to the total power across all channels on other carriers; or it can be a ratio between specific control channels on different carriers.
18. The wireless communication transmitter of claim 12 wherein the multi-carrier transmitter back-off metric estimation circuit is configured to estimate the multi-carrier transmitter back-off metric further based on one or more configuration parameters of a signal on at least one of the carriers.
In the wireless transmitter described above, the back-off estimation circuit also considers the configuration parameters of at least one of the carriers when estimating the overall power reduction. These parameters influence the back-off estimation in addition to the individual carrier metrics.
19. The wireless communication transmitter of claim 18 wherein the one or more configuration parameters comprise gain factors for the physical channels in a Wideband Code-Division Multiple Access (WCDMA) signal, or resource block allocations and modulation scheme in a Long Term Evolution (LTE) signal.
In the wireless transmitter described above, where the back-off estimation circuit uses carrier configuration parameters, the parameters include, for WCDMA signals, the gain factors of the physical channels; or, for LTE signals, the resource block allocations and the modulation scheme being used.
20. The wireless communication transmitter of claim 12 wherein the multi-carrier transmitter back-off metric estimation circuit is configured to base the multi-carrier transmitter back-off metric on a weighted sum of the two or more carrier-specific metrics obtained.
In the wireless transmitter described above, the back-off estimation circuit calculates the overall power reduction by computing a weighted sum of the individual carrier-specific metrics.
21. The wireless communication transmitter of claim 20 wherein the weight applied to each carrier-specific metric is a constant or, alternatively, depends on at least one of: a power ratio between the power of one or more channels on one of the carriers and the power of a corresponding one or more channels on other carriers; or one or more configuration parameters of a signal on at least one of the carriers.
In the wireless transmitter described above, where the back-off estimation circuit uses a weighted sum, the weight applied to each carrier metric can be a fixed constant. Alternatively, the weight can depend on the power ratio between channels on different carriers, or on the configuration parameters of at least one of the carriers.
22. The wireless communication transmitter of claim 20 wherein the weight applied to each carrier-specific metric depends on a power ratio between the power of one or more channels on one of the carriers and the power of a corresponding one or more channels on other carriers, and wherein the multi-carrier transmitter back-off metric estimation circuit is further configured to calculate the weights, or retrieving them from a lookup table, based on the value of the power ratio or, alternatively, based on which one of a plurality of ranges the power ratio falls within.
In the wireless transmitter described above, where the back-off estimation circuit uses a weighted sum and the weights depend on a power ratio between channels on different carriers, the circuit either calculates the weights directly from the power ratio, or looks them up in a table based on the power ratio's value, or the range within which it falls.
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June 22, 2009
June 25, 2013
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